How to start mysql 8? without conflicting with the default mariadb

I tried the following changes to add mysql8.0 support.

diff --git a/bin/ktd b/bin/ktd
index b82936d..9348e22 100755
--- a/bin/ktd
+++ b/bin/ktd
@@ -187,6 +187,9 @@ while [ $# -gt 0 ]; do
         --os2)
             set_searchengine "os2"
             shift ;;
+        --mysql8.0)
+            ENABLE_MYSQL_8_0="yes"
+            shift ;;
         --plugin)
             ENABLE_PLUGIN="yes"
             shift ;;
@@ -244,6 +247,11 @@ else
                 KOHA_ELASTICSEARCH="yes"
             fi
 
+            if [ "$ENABLE_MYSQL_8_0" != "no" ]; then
+                echo $COMPOSE_OPTIONS
+                COMPOSE_OPTIONS="${COMPOSE_OPTIONS} -f docker-compose.mysql8.0.yml"
+            fi
+
             if [ "$ENABLE_PLUGIN" != "no" ]; then
                 COMPOSE_OPTIONS="${COMPOSE_OPTIONS} -f docker-compose.plugin.yml"
             fi

But it fails with validating [...]koha-testing-docker/docker-compose.mysql8.0.yml: services.db.environment array items[0,4] must be unique So it collides with mariadb env vars array being already defined in docker-compose-light.yml

I trying the old way of starting KTD: KOHA_IMAGE=master-jammy docker compose -f docker-compose-light.yml -f docker-compose.mysql8.0.yml -p koha up --force-recreate But unsurprisingly the same error happens.

How does the CI do it? jenkins_config/build.pl seem to end up chaining docker-compose-light.yml and docker-compose.mysql8.0.yml so it should have the same outcome.